The patent is directed to shutters, and more particularly to a rolling protective shutter having a unitized structural frame for mounting the shutter to the structure surrounding and defining an opening to be covered by the shutter curtain, and for reinforcing the side rails and the structural framing of the opening.
Hurricane protection is desired more and more by business owners, home owners and municipalities, and the engineering and testing requirements for such protection are becoming increasingly stringent and rigorous. Many different solutions have been implemented in the attempt to protect structures from the varying forces and conditions associated with hurricanes. For example, openings for windows, doorways, porches and the like require protection from the forces created by the severe winds associated with the hurricanes that cause positive pressure pressing against the openings on the windward side of the structure, and negative pressure pulling outwardly from the opening on the leeward side of the structure.
One attempted solution for protecting openings is the installation of panels attached to the surrounding support structure of the building defining the opening such that the opening is essentially isolated from the surrounding environment. FIG. 1 illustrates an example of a panel 10 configured to cover an opening 12 defined by the surrounding structure 14 and having a window 16 disposed therein. The panel 10 has a plurality of openings 18 around the perimeter of the panel 10 configured to receive fasteners that will anchor the panel 10 to the surrounding structure 14 on the both sides and above and below the opening 12.
The panel 10 may be fabricated from any desired material that may withstand the conditions present during the hurricane, such as metal, plywood, fabric and the like. FIG. 2 schematically illustrates the reaction of the panel 10 fabricated from a rigid material mounted over the opening 12 by fasteners 20 and subjected to a force FNP resulting from the negative pressure caused by high winds during a hurricane. Because the panel is rigid, the panel does not deflect in response to the negative pressure, and the force FNP is distributed relatively evenly to the fasteners 20 and support structure on all four sides of the panel 10 and opening 12. The fasteners 20 primarily experience tensile loads that may be accounted for with adequate numbers and sizes of fasteners 20. FIG. 3 schematically illustrates a flexible panel 10 covering the opening 12 and subjected to the force FNP resulting from the negative pressure. As with the rigid panel 10, the fasteners 20 are placed in tension as a result of the negative pressure. Moreover, because the panel 10 is fabricated from a flexible material, the panel 10 may deflect outwardly due to the force FNP with a catenary cross-section approximating the shape of a sagging bed sheet. The deflection of the panel 10 subjects the fasteners 20 and the support structure 14 to which the fasteners 20 are attached to torsion loads tending to rotate the fasteners 20 and support structure 14 in the direction indicated by the arrows in FIG. 3 and potentially resulting in greater pressures to the fasteners 20 and structure 14. However, as with the rigid panel 10, the design of the flexible panel 10 may account for the torsion loading by providing the requisite numbers and sizes of fasteners 20.
While the negative pressure condition is illustrated, those skilled in the art will understand that similar issues and types of loading are presented by positive pressure on the windward side of the structure during extreme weather conditions. Therefore, the panel 10 flexes or bows inwardly when positive pressure is applied, thereby creating torsion loads on the support structure in the opposite direction as in the illustrated negative pressure condition. Similarly, where a fabric covering is installed over an opening, the surface of the fabric covering is engaged by the edges of the walls surrounding and defining the opening when positive pressure is applied, thereby resulting in the application of torsion loads to the framing structure tending to rotate the structure inwardly.
The panels 10 illustrated in FIGS. 1-3 may be convenient where the openings 12 to be covered are readily accessible for installation of the panels 10, such as at street level. However, the panels 10 are difficult to install over openings 12 on higher floors. Moreover, the size and weight of the panels 10, and the number of fasteners 20 and the manner of their attachment may make the installation and removal of the panels 10 difficult and time consuming. Therefore, as an alternative to such panels, rolling protective shutters have been implemented for protection openings during hurricanes for many years. The rolling protective shutters may be permanently attached to the structure surrounding the openings, and include deployment mechanisms for quickly rolling and unrolling the shutter curtains. One type of known rolling shutter assembly 30 is shown in FIG. 4. The shutter assembly 30 has a shutter housing which includes a top wall 32, a pair of side walls or end caps 34, and a front wall 36. A shutter support member 40 is mounted for rotation within the shutter housing. The support member 40 includes a generally cylindrical central shaft 42 and a plurality of mounting members 44 fixed to the shaft 42. The upper end of a rolling shutter 50 is coupled to the mounting members 44. The shutter 50 is composed of a plurality of individual, elongate slats 52. The ends of the slats 52 are disposed within a pair of shutter tracks or side rails 60.
The illustrated shutter assembly 30 has a gearbox 62 which interconnects the rotatable shaft 42 with a hand crank 64 via a conventional gear assembly (not shown). When mounted to protect a window or other opening, the shutter tracks 60 of the shutter assembly 30 are positioned on either side of the opening and attached to the walls with fasteners, and the shutter housing is positioned over the top of the opening. Alternatively, in some applications, the side tracks 60 and shutter housing are positioned within the opening. When the shutter 50 is not in use, it is rolled up on the shutter support member 40 via the hand crank 64 so that it is at least partially enclosed by the shutter housing. The hand crank 64 may be disposed on a rear portion of the shutter assembly 10 so that the shutter 50, when attached over a window for example, can be unrolled from inside the window. Alternatively, when the gearbox 62 is not provided, the support member 40 may include a torsion spring. The shutter 50 may be rolled and unrolled with the assistance of the tension in the spring by exerting a force on a bottommost slat 66 by grasping a handle 68 that extends longitudinally along the slat 66 and outwardly from the shutter 50. Other drive mechanism, such as straps, tubular operators and motors are well known in the art and are used to open and close rolling shutters.
FIG. 5 schematically illustrates the shutter assembly 30 wherein the tracks 60 receive and guide the ends of the slats 52, and FIG. 6 schematically illustrates the reaction of the shutter 50 to the force F.sub.NP resulting from the negative pressure caused by the high winds during a hurricane. The side tracks 60 are secured to the corresponding support structures defining the left and right sides of the opening 14. In the normal position of FIG. 5, the shutter curtain 50 is not under tension so the ends of the slats 52 are fully extended into the side tracks 60. When the shutter curtain 50 is subjected to the force FNP as shown in FIG. 6, the shutter curtain 50 bows outwardly due to the force FNP thereby reducing the width of the shutter curtain 50 until one or both ends of the shutter curtain 50 pull free from the side tracks 60. While the shutter curtain 50 remains in the side tracks 60, the side tracks 60, fasteners 70 and corresponding support structures are subjected to the tensile and torsion loading as indicated by the arrows in FIG. 6. However, the loads created on the side tracks 60, support structures 14 and fasteners 70 typically do not cause catastrophic failures of those elements because the shutter curtain 50 will pull free from the side tracks 60 before the loading becomes too great.
Some panels as discussed above and other types of shutters exert their loads evenly on all sides simultaneously, thereby balancing the load on all sides. This may occur in panels and shutters having high levels of rigidity. The fasteners are subjected only to tension loading when the panel or shutter is subjected to negative pressure. Fasteners are designed with pull out ratings and are easily tested when subjected to this type of pressure. Rolling shutters as discussed above exert more pressure on the structure and fasteners due to their design. Until recently, rolling shutters were only able to span small openings for hurricane protection due to many factors. One factor is the issue of pull out of the shutter curtain as discussed above. Additionally, the housing at the top of the assembly 30 provides minimal structural support for the assembly 30, and the bottommost shutter slat 66 is typically not attached to the structure surrounding the opening 14 in a manner that provides structural support. Due to this, the side tracks 60 are the only components of the assembly 30 supporting the loading caused by pressure on the shutter curtain. The rolling shutter is not able to balance the pressures and loads on all four sides. Another problem arises from the planar profile and relatively small cross section of the rolling shutter curtain 50. The shutter curtain 50 is very flexible, and as it flexes, unless it is retained in the track in some manner, is easily pulled from the side tracks 60.
To prevent the shutter curtain 50 from pulling out of the side tracks 60 and to increase the capacity of the shutter curtain 50 to withstand positive and negative pressure loading during extreme conditions, end retention systems have been developed to hold the two ends of the slats 52 captive within the side tracks 60. FIGS. 7 and 8 illustrate an example of shutter slats 80 and a corresponding side track 100, respectively, configured to retain the ends of the slats 80 within the side track 100 when forces tend to cause the shutter curtain 50 to bow. Referring to FIG. 7, each slat 80 includes a double-wall slat portion 82, and is arc-shaped to facilitate rolling the shutter curtain onto the shutter support member 40. Each slat 80 further includes an elongated socket 84 integrally formed along the bottom edge 85 of the slat portion 82. A rod 86 is integrally formed along the top edge 87 of the slat portion 82. The rod 86 includes a groove or channel formed therein and running along the longitudinal length of the rod 86 to form an integral screw boss 88. The combined rod 86 and screw boss 88 approximate the shape of a second, smaller socket integrally formed on the edge 87 of the slat portion 82. The slats 80 are typically fabricated from extruded aluminum or polyvinyl chloride, but other materials and fabrication methods are known in the art.
The slats 80 are fabricated such that the inner diameter of the socket 84 is slightly larger than the outer diameter of the rod 86. The shutter curtain is assembled by sliding the rod 86 of one slat 80 into the socket 84 of the adjacent slat 80. The slats 80 are oriented with their concave surfaces on the same side of the shutter curtain so that the curtain rolls up properly onto the shutter support member 40. When the slats 80 are assembled, the rods 86 are pivotal within the sockets 84 to facilitate movement of the shutter curtain between the rolled and unrolled positions. Since the sockets 84 cover over half the diameter of the rods 86, the rods 86 are permanently retained within the sockets 84. The sockets 84 and rods 86 are configured to form a hinge that allows the connected slats 80 to rotate between a first position in which the sockets 84 and the rods 86 of the slats 80 are substantially linearly aligned, and a second position wherein the slat portions 82 combine to define an arc.
Once the shutter curtain is assembled, extension members 90 are attached to the screw bosses 88. The extension members 90 are adapted to keep the slats 80 vertically aligned and to captivate the shutter curtain within the side tracks 100 to prevent the shutter curtain from pulling out of the side tracks 100 during either an attempted break in or extreme wind conditions. Each of the extension members 90 has an inner flange 92 and an outer flange 94 separated by a neck 96 having a smaller diameter than the flanges 92, 94. Each extension member 90 further includes a threaded shank 98 that is dimensioned to correspond to the screw boss 88. The extension members 90 are attached to the shutter curtain by screwing the shanks 98 into the screw bosses 88 so that the extension members 90 are attached to both ends of a given screw boss 88.
The extension members 90 extend outwardly from the shutter curtain and the outer flanges 94 are captivated by the side tracks 100, as shown in FIG. 8, and prevent the shutter curtain from being pulled out of the shutter tracks 100. Each side track 100 has a pair of side walls 102, 104, and an end wall 106. The side track 100 further includes a pair of fins 112, 114 that extend inwardly from the side walls 102, 104, respectively, and define a gap 116 wide enough to receive the neck 96 of the extension member 90. The neck 96 of the extension member 90 extends through the gap 116 so that the outer flange 94 is disposed on the opposite side of the fins 112, 114 from the inner flange 92 and slat 80. The diameter of the outer flange 94 is larger than the gap 116 between the fins 112, 114 so that the outer flange 94 cannot be pulled through the gap 116. When the shutter curtain is subjected to a force perpendicular to its surface, such as the force FNP of the negative pressure generated during a hurricane as shown in FIG. 9, the slats 80 bow and the ends of the slats 80 move toward the opening in the side tracks 100. As the slats 80 bow, the outer flanges 94 of the extension members 90 are engaged by the fins 112, 114 of the side track 100 to retain the ends of the slats 80 within the side track 100. Similarly, the slats 80 bow inwardly when sufficient positive pressure is applied to the shutter curtain.
Other examples of slats for rolling shutter curtains configured to receive retention mechanisms for retaining the ends of the shutter curtains within the side rails can be found in U.S. Pat. No. 6,095,224, entitled “Shutter Tracks for Rolling Protective Shutters,” U.S. Pat. No. 6,095,225, entitled “Shutter Slat with Integrated Screw Boss,” and U.S. Patent Publication No. 2005/0205221 A1, entitled “Dual Boss Shutter Slat with Retention Plate,” the entire disclosures of which are incorporated herein by reference. In each case, retention members are connected to the ends of the slats of shutter curtains, and the side tracks are configured to engage the retention members and retain the ends of the slats within the side tracks.
Rolling shutters incorporating end retention are capable of withstanding higher pressures without the shutter curtain being pulled out of the side tracks than they had in the past. As a result, not only must the shutter curtain be designed and engineered to withstand the increased loading, but consideration must also be given to the relationship between the rolling shutter assembly and the building structure to which it is attached. Depending on the construction of the structure to which the rolling shutter is attached, the support structure may be the likely point of failure when the rolling shutter is subjected to extreme conditions. Sufficiently strong framing may not be available in buildings constructed without consideration to supporting the types and magnitudes of loading that the rolling shutters are designed to withstand. New construction may be able to take such loading into consideration, but existing construction may not.
For example, FIGS. 2, 3, 5, 6 and 9 schematically illustrate a wood framed house that is typical in many areas of the East Coast of the United States. The houses were designed before consideration of hurricane protection. Since glass is very rigid, and transfers weight evenly and in one direction, and has very little catenary reaction on the jambs, very few structural 2×4's were needed to provide the structural framing. Due to the amount of catenary force applied to the frame by today's rolling shutter systems, an opening of 5 feet could require four 2×4's to provide the minimum required wind protection. Unfortunately, most existing wood framed houses are not constructed with the required number of 2×4's. Due to this, many times the fasteners do not fail but the jamb fails.
Rolling shutter assemblies with end retention create problems that are unique as compared to many other types of shutter systems and protective panels, and that make these assemblies inappropriate for many applications. As discussed, the loads are concentrated on the sides tracks of the assembly. Moreover, the side tracks, fasteners and the structure of the building are subjected to torsion loading due to the simultaneous retention and bowing of the shutter curtain under pressure loading. The torsion loading is more severe than normal tension and sheer loading encountered by other shutters and panels. Since virtually all of the loading is supported by the two side tracks and the structure to which they are attached, it is extremely critical that the structure can withstand these highly concentrated loads. Consequently, a need exists for a rolling shutter that may be able to withstand pressure loading applied to the shutter curtain while transferring a reduced amount of the loading to the portions of the support structure to which the side tracks are attached. As noted above, though, flexible panels and fabric covers can also cause torsion loading on the support structure around the opening. Therefore, a need also exists for reducing the torsion loads transferred to the supporting structure by these types of coverings.
In certain situations, deflection of the shutter curtain needs to be minimized when subjected to positive pressure, negative pressure, or both. For example, sometimes the pressure loads applied by hurricane-force winds must to be redistributed from the framing to which the side tracks of the shutter assembly are attached to other portions of the support structure of the building. In these installations, a storm bar system may be used to redistribute the pressure loads. The ends of the storm bar are attach at either side of the rolling shutter so that the storm bar extends across and engages the shutter curtain to provide additional support for the pressure loads, and the storm bar may be fixed or removable. When the storm bar is oriented parallel to the side tracks and disposed on the coil side of the shutter curtain, a storm bar header is used to secure the top end of the storm bar.
Because the shutter curtain must be free to roll up and unroll, the storm bar header must be secured to the support structure at locations beyond the outer edges of the slats. Due to the required fasteners, many times the storm bar header may be longer than the shutter assembly. Moreover, the distance between the storm bar and the points of attachment of the storm bar header is also a problem in wood framed structures because the torsion loads at the ends of the storm bar header may be too great for the wood framing to support. Still further, the building may not have the required support structure beyond the width of the shutter assembly, or an adjacent shutter or other structure may restrict the ability to attach the storm bar header in the manner necessary to support withstand the required magnitude of pressure loading. Therefore, a need also exists for a mechanism for adequately securing a storm bar header for a rolling shutter in diverse configurations of support structures.